The present invention relates to sensing angular rotation of an object, and particularly relates to sensing angular rotation of an object for use in detecting a vehicle rollover condition.
In order to detect an occurrence of a vehicle rollover it is known to equip a vehicle with a sensor for detecting the occurrence of a condition that is indicative of a vehicle rollover. The sensor, which typically includes one or more acceleration sensing devices, is connected to a controller. The sensor provides a signal that has a characteristic indicative of vehicle rollover to the controller. The controller, in turn, determines the occurrence of a vehicle rollover condition based on the sensor signal. The controller also may control actuation of one or more actuatable devices, such as an occupant restraint and/or an active suspension system, in response to determining the occurrence of a vehicle rollover condition. For example, U.S. Pat. No. 5,825,284 discloses a vehicle system having a sensor that provides a signal indicative of lateral acceleration of the vehicle. A processor is connected to the sensor for calculating a roll moment based on the sensor signal. The system includes a display device that visually displays an indication of the likelihood of a vehicle rollover condition based on the calculated roll moment.
Various devices also have been proposed for detecting angular orientation of an object. For example, U.S. Pat. Nos. 5,329,121, 4,207,463, 5,670,780, 5,103,090, and 4,320,293 disclose rotation angle measuring devices that sense rotation of a body using optical emitters and detectors.
In accordance with a one aspect, the present invention provides an apparatus for sensing angular rotation. The apparatus includes a rotor that is rotatable about an axis. The rotor has an outer periphery with a plurality of reflective facets. Each juncture between each adjacent pair of the facets defines a vertex. A light source emits a light beam onto the rotor. The light beam from the light source is reflected by the facets and occasionally bifurcated by the vertices. A light detector detects the reflected light and provides a detector signal indicative of angular rotation of the rotor and the bifurcation. Compensation circuitry, responsive to the detector signal, compensates for the bifurcation and provides a compensated output signal indicative of the angular rotation of the rotor.
In accordance with another aspect, the present invention provides a rollover sensor for a vehicle. The sensor includes a rotor that is rotatable about an axis and that has an outer periphery with a plurality of reflective facets. Each juncture between each adjacent pair of facets defines a vertex. A light source emits a light beam onto the rotor. The light beam from the light source is reflected by the facets and occasionally bifurcated by the vertices. A light detector detects the reflected light and provides a detector signal indicative of angular rotation of the rotor and the bifurcation. Compensation circuitry, responsive to the detector signal, compensates for the bifurcation and provides a compensated output signal indicative of angular rotation of the rotor. A controller determines an angular velocity of the vehicle based on at least one of the compensated output signal and the detector signal. The controller determines a vehicle rollover condition based on the determined angular velocity of the vehicle.
In accordance with still another aspect, the present invention provides an apparatus for sensing angular rotation. The apparatus includes rotor means for rotating about an axis. The rotor means has an outer periphery with a plurality of reflective members. Each juncture between each adjacent pair of the reflective members defines a vertex. Emitter means emits a beam onto the facets of the rotor means. The emitted beam is reflected by the facets and occasionally bifurcated by the vertices. Detector means detects the reflected beam and provides a detector signal indicative of angular rotation of the rotor means and the bifurcation. Compensation means, responsive to the detector signal, compensates for the bifurcation and provides a compensated output signal indicative of angular rotation of the rotor means.
In accordance with yet another aspect, the present invention provides a method for sensing angular rotation of an object. A rotor is mounted for rotation relative to the object that is in response to movement of the object. The rotor has an outer periphery with a plurality of reflective members. Each juncture between each adjacent pair of the reflective members defines a vertex. An emitted beam is emitted onto the rotor. The emitted beam is reflected by the reflective members and occasionally bifurcated by the vertices. The reflected light is detected and a detector signal that is indicative of angular rotation of the rotor and bifurcation is provided. The bifurcation is compensated and a compensated output signal indicative of angular rotation of the rotor is provided.